1. Field of the Invention
The present invention relates to studs and to associated stud hardware. More particularly, the present invention relates to stud hardware with a self-contained anti-rotation feature.
2. Background of the Invention
A stud as used herein is essentially a threaded rod which may have a head portion on one end and which is assembled into a tapped hole, the other end receiving a nut. Alternatively, the stud may have two head portions with the member(s) to be clamped positioned therebetween. In order to properly secure a stud from becoming loose, it or its associated nut must be tightened so that at normal torque, compressive, and tensile loads, and in the temperature range to be experienced, it has been sufficiently preloaded to obviate an accidental loosening. Several ways have been devised for applying a preload to a stud. Two ways of effecting a preload on a stud involve the application of a tensile or torque load. The stud may be stretched by use of hydraulics or other mechanical or thermal means and the nut threaded down to bottom onto the fastened part. An alternative method is purely manual and involves holding the stud stationary while the nut is torqued to a predetermined value or rotated through a set distance.
When torque is applied to the nut to effect stud preload two operators are usually required, especially when the desired preload is high. A first operator must turn the nut while the other restrains the stud from rotation. For rare situations, when the correct physical conditions exist, the operator securing the stud from rotation can be eliminated by "blocking" the end of the wrench securing the stud to a stationary object. In the majority of cases, however, this is not possible.
In addition, in prior designs, problems arose when high torque preloads were required or when studs were not perfectly aligned in the holes of the part to be fastened or when the rotational orientation of the stud was crucial based upon the required "stack-up" height or based upon the stud bottom thread shear strength.
U.S. Pat. No. 514,315 to L. D. Frenot discloses a lock nut used in association with a bolt having both right and left hand screw thread extending along a side of two nuts provided with right and left screw threads, respectively, which are adapted to fit the corresponding threads on the bolt. The nuts have indents and detents so that when securely mated, they will cooperate to hold each other against rotation. Such an arrangement may require as many as three operators to install, requires complicated machinery and customized threading of the bolt. The hardware is expensive and requires an excessive amount of intensive work to install accurately, and consistently in those applications where many such bolt-nut combinations must be installed.
In U.S. Pat. No. 2,295,466 to J. Hafele there is disclosed a bolt and nut connection which is secured against rotation by a washer having a projection which keys into the work piece being held by the bolt. A plate is used which must be constructed with a resilient washer portion with an opening shaped to fit that of the nut or other fastening element which is secured onto the bolt. The washer or plate must be provided with ribs which engage corresponding ribs on the washer in such a way as to restrain the washer and plate from separating. The invention, therefore, requires many precision parts which require very specialized construction and which require the excessive expenditure of valuable skilled labor time on the part of two operators to properly install.
Neither of these references discloses any means for preloading studs or an effective and efficient way to repetitively preload large numbers of studs.